Venipuncture and peripheral intravenous catheter insertion are routine medical procedures performed to collect blood samples, and to administer medications or body fluids. In 2008, there were about 37.5 million hospital admissions in the U.S., and almost every hospital patient can have at least one blood draw on admission. Additionally, 7 out of 10 patients can receive an IV, and 3 out of 10 patients can get an injection of contrast, which can total a minimum of 263 million vein access procedures in the year 2008 alone. This figure does not include any vein access procedures done during an out-patient procedure. Based upon the industry's recognized vein access failure rate of about 40%, which can result in a multiple stick event for 4 out of every 10 patients (e.g., on every stick attempt), this adds up to a minimum estimate of 174 million vein access failures divided between the IV, the blood draw, and the injection of contrast. (See, e.g., The National Phlebotomy website (http://www.nationalphlebotomy.org/).
An extraction of blood from a peripheral vein, or the insertion of catheter, usually benefits from a distention of superficial veins in the arm. For a successful venous distention, the venous flow should be occluded while the arterial flow should unhinder. Ideally, for example, the optimal venous distension can be caused by applying a pressure between the systolic and diastolic pressures.
The current technique for accessing an extremity vein includes placing a tourniquet proximal (e.g., nearer the heart) on the extremity. The tourniquet is most commonly made of an elastic material (e.g. a rubber glove, or a rectangular piece of elastic material), and as such, it can be difficult or even impossible to measure the pressure applied. Therefore, the applied pressure can be above the arterial systolic pressure, which can result in no blood inflow, or the pressure can be below the arterial diastolic pressure, facilitating venous outflow. In both cases, venous distension may not occur. An optimal pressure for the tourniquet would be below the systolic pressure (e.g., the peak arterial pressure), and above the diastolic pressure (e.g., the venous pressure). Applying this pressure can facilitate an arterial inflow, but would likely not facilitate a venous outflow, thereby leading to the distension of the circulation.
The pliable strap or latex strip tourniquet can be commonly used by positioning it around the arm of the patient. Both ends can be grasped and tied to apply a small amount of tension. It can be the least expensive, and is a disposable tourniquet, and it can prevent cross infection of patients, as it does not readily support bacterial growth because of the material property of latex. In addition, it can be easily cleaned with any disinfectant. However, the pliable strap tourniquet cannot be loosened gradually, which can pinch the skin on elderly patients. It also needs nurses and technicians to use both hands for proper positioning.
A Velcro® closure tourniquet can be made of elastic material with a long band that facilitates a wider range of adjustments. Generally, the Velcro® tourniquet can be more expensive than the pliable strap tourniquet. It can be easily cleaned with any disinfectant. In addition, the Velcro® tourniquet can be easier to apply and release than the pliable strap tourniquet. The Velcro strap, however, cannot be loosened gradually, and it also likely needs using both hands for proper positioning.
The buckle closure tourniquet can be made of cloth fabric with a buckle closure (e.g., seat-belt design). It can be gradually loosened and tightened again, if necessary. Unlike the tourniquets above, it may not be disposable, and cannot be easily cleaned with disinfectants. Generally, the buckle closure tourniquet is not commonly used because of its high cost and restricted usage.
A common blood pressure cuff can be used as a tourniquet. The cuff can be inflated to a pressure between the systolic and diastolic pressures for venous distension. It can be useful among patients with weak veins that can be difficult to see with the naked eyes. Blood pressure cuffs usually include a sphygmomanometer, thus, the applied pressure can be readily known.
In the surgical setting, surgical tourniquets can be applied to the limb occlusion pressure (“LOP”), the minimum pressure used to occlude a patient's limb completely, to localize anesthesia drugs and to provide a bloodless operating field during surgeries. There are many different surgical tourniquet systems. A surgical tourniquet can consist of an instrument for pressure regulation, and an inflatable cuff for pressure application. It can be designed to measure the LOP using the ascending LOP measurement technique. The ascending LOP measurement can determine the LOP by slowly increasing pressure in the cuff until the LOP can be reached.
This surgical tourniquet generally requires the surgical staffs to enter an estimated LOP value. This LOP value can be set as the reference pressure, and can be regulated by a controller during surgeries every 40 millisecond with the allowed deviation of ±15 mmHg. A pulse oximeter can be utilized as a means to adjust the preset reference pressure. The pulse oximeter can be composed of an infrared LED with wavelength of about 915 nm, and a photodiode that can be sensitive to that wavelength. The basic principle of pulse measuring can be based on the absorption of infrared light by oxygenated hemoglobin. Based on oxygenated hemoglobin concentration, current can be produced by the photodiode. This current can be filtered, sampled and analyzed by the controller. However, concentration of oxygenated hemoglobin in the extremity can be time-varying, in synchrony with the cardiac cycle. As a result, time-varying current signifies incomplete occlusion of arterial flow. The preset reference pressure can be adjusted according to the pulse detection in the extremity. A new reference pressure can be obtained when no time-varying current can be detected. This pressure will be the LOP and it will be maintained until the end of surgeries. The A.T.S. 3000 Automatic Tourniquet System is a medical tourniquet system with a processor controlling two air pressure ports at each cuff. One port can be used for pressure measurement, while the other port regulates cuff pressure. It uses a LOP sensor at the patient's index finger or toe to provide a recommended LOP to the surgeon. However, this pressure can be used to completely occlude the patient's limb.
Thus, it may be beneficial to provide an exemplary pressure sensitive device that can reduce the rate of vein access failure for an individual patient's blood pressure, and which can overcome at least some of the deficiencies described herein above.